Polymerization of Hydroxy-Containing Diazoacetates: Synthesis of Hydroxy-Containing “Poly(substituted methylene)s” by Palladium-Mediated Polymerization and Poly(ester–ether)s by Polycondensation through O–H Insertion Reaction

Phase Behaviors and Photoresponsive Thin Films of Syndiotactic Side-Chain Liquid Crystalline Polymers with High Densely Substituted Azobenzene Mesogens

Azobenzene-containing polymers (azopolymers) are a kind of fascinating stimuli-responsive materials with broad and versatile applications. In this work, a series of syndiotactic C1 type azopolymers of Pm-Azo-Cn with side-chain azobenzene mesogens of varied length alkoxy tails (n=1, 4, 8, 10) and different length alkyl spacers (m=6, 10) have been prepared via Rh-catalyzed carbene polymerization. The thermal properties and ordered assembly structures of thus synthesized side chain liquid crystalline polymers (SCLCPs) have been systematically investigated with differential scanning calorimetry (DSC), polarized optical microscopy (POM) and variable-temperature small/wide-angle X-ray scattering (SAXS/WAXS) analyses. P10-Azo-C1 and P10-Azo-C4 with shorter alkoxy tails exhibited hierarchical structures SmB/Colob and transformed into SmA/Colob at a higher temperature, while P10-Azo-C8 and P10-Azo-C10 with longer alkoxy tails only displayed side group dominated layered SmB phase and transformed into SmA phase at higher temperatures. For P6-Azo-C4 with a shorter spacer only showed a less ordered SmA phase owing to interference by partly coupling between the side chain azobenzene mesogens and the helical backbone. More importantly, the series high densely substituted syndiotactic C1 azopolymer thin films, exhibited evidently and smoothly reversible photoresponsive properties, which demonstrated promising photoresponsive device applications.

Reactivity of poly(alkoxycarbonylmethylene)s under basic conditions: alkylation of main chain carbon atoms via a ketene silyl acetal-type intermediate and cleavage of the carbon–carbon main chain

We report the alkylation of main chain carbon atoms and cleavage of the carbon–carbon main chain of poly(alkoxycarbonylmethylene)s.

Effects of solvents, additives, and π-allyl ligand structures on the polymerization behavior of diazoacetates initiated by π-allylPd complexes

We have revealed that the quality of control of the polymerization was improved by adding some compounds and polymer tacticity was dependent on the structures of π-allyl ligands.

Polycondensation of bis(α-diazo-1,3-dicarbonyl) compounds with dicarboxylic acids: an efficient access to functionalized alternating polyesters

We report an efficient and mild approach to functionalized alternating polyesters on the basis of O–H insertion polycondensation of bis(α-diazo-1,3-dicarbonyl) compounds with dicarboxylic acids.

Palladium-catalyzed carbene coupling of N-tosylhydrazones and arylbromides to synthesize cross-conjugated polymers

Palladium-catalyzed cross-coupling reactions of N-tosylhydrazones and arylbromides have been applied for the first time in the synthesis of cross-conjugated polymers, namely poly(arylene-1,1-vinylidene)s (iso-PAVs).

Aqueous Phase Separation Behavior of Highly Syndiotactic, High Molecular Weight Polymers with Densely Packed Hydroxy-Containing Side Groups

Herein we describe the Rh-catalyzed C1 polymerization of silyl-protected diazoacetates of the general formula HC(=N₂)C(=O)O(CH₂) _x OSiR₃, where x = 2-5. After polymerization and subsequent desilylation, syndiotactic polymers bearing a hydroxy-containing side group on every backbone carbon are obtained. The molecular weight of the desired polymers can be controlled via chain transfer with methanol during the polymerization. The produced polymers are compared to atactic analogues formed by [(η³-C₃H₅)PdCl]-catalyzed polymerization of silyl-protected diazoacetates with the same general formula. While the polymers produced by the Rh and Pd catalysts have the same hydrophilic/hydrophobic balance, the stereoregularity of the polymers formed by the Rh catalyst was found to be of influence on the thermoresponsive behavior of the polymer. The effect of this stereoregularity on the thermoresponsive phase separation behavior of the produced polymers in aqueous solution was investigated.

Self-Assembly of Hierarchical Structures Using Cyclotriphosphazene-Containing Poly(substituted methylene) Block Copolymers

The cyclotriphosphazene-substituted diazoacetate homopolymer (polyPNDA') (PNDA' = hexaphenoxy-substituted phosphazene-containing methylene) and a novel poly(substituted methylene) block copolymer, polyPNDA'-block-poly(hexyloxycarbonylmethylene) (polyPNDA'-b-polyHDA'), were synthesized, and the self-assembly behavior of these polymers was studied in detail. A hexagonally packed aggregated structure was observed in the self-assembled structure of polyPNDA', whereas a lamellar structure was observed in the microphase-separated nanoassembly of polyPNDA'-b-polyHDA'. These results indicate that a hierarchical structure composed of highly regular polyPNDA' nanoaggregates and the long-range microphase-separated polyPNDA' and polyHDA' domains had formed.

Migratory Insertion of Carbenes into Au(III)-C Bonds

Migratory insertion of carbon-based species into transition-metal-carbon bonds is a mechanistic manifold of vast significance: it underlies the Fischer-Tropsch process, Mizoroki-Heck reaction, Ziegler-Natta and analogous late-transition-metal-catalyzed olefin polymerizations, and a number of carbonylative methods for the synthesis of ketones and esters, among others. Although this type of reactivity is well-precedented for most transition metals, gold constitutes a notable exception, with virtually no well-characterized examples known to date. Yet, the complementary reactivity of gold to numerous other transition metals would offer new synthetic opportunities for migratory insertion of carbon-based species into gold-carbon bonds. Here we report the discovery of well-defined Au(III) complexes that participate in rapid migratory insertion of carbenes derived from silyl- or carbonyl-stabilized diazoalkanes into Au-C bonds at temperatures ≥ -40 °C. Through a combined theoretical and experimental approach, key kinetic, thermodynamic, and structural details of this reaction manifold were elucidated. This study paves the way for homogeneous gold-catalyzed processes incorporating carbene migratory insertion steps.

Polymerization of alkyl diazoacetates initiated by the amidinate/Pd system: efficient synthesis of high molecular weight poly(alkoxycarbonylmethylene)s with moderate stereoregularity

The initiating ability of a new system, amidinate/Pd, for the polymerization of diazoacetates is described.

Synthesis of poly(allyl 2-ylidene-acetate) and subsequent post-polymerization modification via thiol–ene reaction

Poly(allyl 2-ylidene-acetate) (M_w = 125 300 g mol⁻¹) was synthesized via rhodium mediated catalysis of allyl 2-diazoacetate and its polymerization kinetics and polymer characteristics are presented and discussed. Furthermore, post-polymerization modification utilized the reactive character of poly(allyl 2-ylidene-acetate) by means of thiol–ene reactions.

One-pot catalyst-free synthesis of down- and upconversion fluorescent oligopyrazolines from diazoacetates and maleic anhydride

Oligopyrazoline, synthesized conveniently from maleic anhydride and diazoacetates via a one-pot catalyst-free reaction, exhibits fascinating down- and upconversion fluorescence properties.

Pd-initiated controlled polymerization of diazoacetates with a bulky substituent: synthesis of well-defined homopolymers and block copolymers with narrow molecular weight distribution from cyclophosphazene-containing diazoacetates

Pd-initiated polymerization of cyclophosphazene-containing diazoacetates proceeded in a controlled manner.

Synthesis of polymers with densely-grafted oligo(ethylene glycol)s by Pd-initiated polymerization of oxyethylene-containing diazoacetates

The polymers with densely-grafted OEGs showed higher LCSTs and Li-ion conductivities than the corresponding vinyl polymers.